The greatest Royal/Met

A while ago I wrote a little Python code that used career data from Baseball-Reference Play Index (the best $36/year a number-loving baseball fan can spend) to answer the question: given a pair of teams, which player contributed the most to both teams? My metric for this is

(WAR for team 1 * WAR for team 2)

in order to privilege players who balanced their contributions to both teams.

So who was the greatest Royal/Met? In retrospect, this should have been obvious. How many of the top 5 can you guess?